1. Field of the Invention
The present invention relates to mobile communications and, more particularly, to communications between mobile stations and emergency service providers.
2. Description of Related Art
The advent and growth of wireless communications has ushered in a new era of convenience and productivity. Interactions that once commonly required a landline connection to a communications network are now possible with seeming disregard for physical location and physical connections. Today, it is possible for a user operating a suitable mobile terminal to engage in both voice and data communications at virtually any location. Personal and business communications can therefore be conducted more quickly and with far fewer restrictions than previously possible.
The widespread use of mobile stations (such as cellular telephones and personal digital assistants (“PDAs”) for instance), however, has been a mixed blessing for emergency service providers, such as 911 centers.
In the past, calls to 911 centers would originate strictly from landline telephones associated with fixed locations such as houses or places of business. Pursuant to government regulations, when a telephone carrier connects such a landline call to a 911 center, the carrier must provide the 911 center with an indication of where the caller is located, as indicated by static directory tables. When a person would call a 911 center from a mobile station, however, a carrier would not provide the 911 center with the caller's location, so the 911 center would not be able to readily find the caller. On the other hand, provided with a mechanism to identify the location of a mobile 911 caller, emergency services would be able to quickly find and respond to emergencies in remote locations.
In the mid-1990s, the United States Federal Communications Commission (“FCC”) addressed this problem, mandating the implementation of “Enhanced 911” (“E911”) services. The E911 mandate was divided into two phases. According to Phase 1, a wireless cellular carrier would be obligated provide a 911 center with an indication of the cell and sector in which a mobile 911 caller is located. As this information is typically maintained by a wireless cellular carrier in a subscriber's home location register (“HLR”), Phase 1 presents little technical challenge. According to Phase 2, the location must be provided with an accuracy of at least 100 meters (or 50 meters for handset-originated methods), which is far more granular than the cell and sector information maintained in the HLR. In response, the Telecommunications Industry Association (“TIA”) has proposed a new standard for “Enhanced Wireless 9-1-1, Phase 2,” now entitled “Wireless Enhanced Emergency Services” or “TIA/EIA/IS-J-STD-036” (J-STD-036), the entirety of which is hereby incorporated by reference.
In order to achieve the accuracy specified by Phase 2, a cellular wireless network may employ special position determining equipment (“PDE”) and techniques. Alternatively, a mobile station itself may employ a position determining system such as the global positioning system (“GPS”) and may relay its position to the network, for reference by the emergency services. The emergency services may then use the position of the mobile station to help assist a user of the mobile station.
The public is increasingly aware that it is now possible to place 911 calls from cellular telephones. At the same time, the popularity and pervasiveness of cellular telephones continues to grow. The end result is that, when an emergency occurs, 911 centers are often barraged with mobile 911 calls from people in the area of the emergency. For instance, if a car accident occurs on a crowded highway, many of the drivers who pass by the accident will call 911 from their cellular telephones, even though it would suffice for just one person to call.
Practically speaking, this presents a problem for 911 service providers. If a mass of calls comes in to a 911 center from a particular area, it is possible that other legitimate emergency calls from around that same area will be blocked (since the PSTN trunks or other transmission channels extending to or from the 911 center might be filled to capacity). For example, if a car accident occurs on a highway and many drivers on the scene call 911, a person suffering from a heart attack in a house adjacent to the accident scene may be unable to contact the 911 center.
Further, once a 911 center learns of an emergency situation that has occurred at a particular location, and particularly once the 911 center has received several calls reporting the emergency, chances are that the 911 center will have already dispatched emergency service personnel. It may therefore be unnecessary to trouble the 911 center with additional calls from the same location.
In view of this problem, a need exists for a method of handling heavy call loads to emergency service centers.